This invention relates to the control network in a light duty motor vehicle, such as a van, minivan, or sport utility vehicle, and, in particular, to a shunt for emulating a removed front seat.
Modern automobiles are endowed with a plurality of computers and sensors to provide convenience and safety for drivers and passengers. These computers are distributed throughout the vehicle communicate with each other via one or more networks. For example, a computer controlling the instrument panel may sense that the vehicle is moving rapidly enough to lock the doors and will signal the appropriate computer that it is time to lock the doors.
Some of the computers provide protection and safety for the driver and passenger. A computer determines, for example, whether the seat belt has been fastened, whether or not there is a person in the passenger seat, and the weight of the person in the passenger seat. Each of these parameters or measurements is performed by sensors located in or near the seat.
The amount of data that is generated and communicated is greater for a passenger's seat than for a driver's seat. If a driver inserts a key into the ignition, then the appropriate air bags will be enabled and the seat belt will be checked for being buckled. However, the presence of mass or a live body in the passenger seat is ambiguous. The passenger side air bag should only be activated if there is a person in the passenger seat and only if that person has a height and weight greater than certain minimums. Hence, the number and sophistication of sensors in the passenger's seat are usually greater than those for the driver's seat.
Typically, sensors, and sometimes their network interfaces, are built into the seat itself and coupled to other computers within the vehicle. If a front seat is removed, the absence of the sensors will be noted by other computers in the vehicle and error signals (visual and audible) will be generated as long as the sensors are missing. One must do something to suppress the error signals without compromising the safety of the vehicle.
Driver side sensors can be transferred to a new seat or passive devices can be added to emulate the driver's seat to prevent detecting false errors. For the driver's seat, the typical OEM (original equipment manufacturer) sensors are the seat belt buckle, air bag sensor, and seat position. These sensors can usually be replaced by passive networks of resistors and/or capacitors to suppress the vehicle warning system. The passive network can often be contained in a small module that plugs into the OEM wiring harness ending at the driver's seat.
The passenger seat, on the other hand, typically has sensors for the seat belt, air bag, adult passenger detection, and weight sensor. The first two sensors are coupled to computers under the seat, while the last two sensors are coupled by network to other computers. The first two sensors can be replaced with passive networks but the last two cannot. The data stream from the passenger sensor and weight sensor must represent occupancy as if the seat were still in place. The problem is further complicated by the fact that some manufacturers uniquely identify each seat with a code that also must be received on a regular basis by other computers in one or more networks. That is, not only must the data be present but it must be present on the correct network at the correct time and preceded by the correct identification code.
For aftermarket outfitters modifying light duty motor vehicles, the problem of removing a front passenger seat, or otherwise removing sensors from a vehicle, is compounded by a lack of information from an OEM, generally because of concern for product liability in a judicial system where outcome can be very unpredictable.
In digital systems, binary data can only represent one of three things: data, an address, or an instruction. This is the information that is carried on a serial data bus or network as used in modern vehicles. The binary data is sent along the serial bus in a format specified by one organization or another. The J1850 standard is from the Society of Automotive Engineers (SAE). Another standard is ISO9141. Control signals are not on the serial bus, at least not directly. Control information can be passed along a network as an instruction to be executed but the wire, the physical bus itself, cannot also be a control line. Conversely, a control line is not a data bus. Collectively, control lines, lines supplying power or ground, and data buses are referred to as the “wiring harness” of a vehicle.
As used herein, no distinction is made among the terms “computer,” “microprocessor,” and “microcontroller.” Similarly, a microprocessor can be a single integrated circuit or a “chip set,” having plural integrated circuits. Microprocessors are produced in a variety of capabilities and one of ordinary skill in the art can readily choose an appropriate device. Most manufacturers produce guides for choosing a device.
In view of the foregoing, it is therefore an object of the invention to provide a shunt for emulating circuitry that has been disconnected from the wiring harness of a light duty motor vehicle.
Another object of the invention is to provide a shunt that can emulate a circuit even when the meaning of signals within the circuit is not understood.
A further object of the invention is to provide a shunt that can be programmed in the vehicle for which it is to be used.
Another object of the invention is to provide a shunt that can adapt to identification or other unique codes circulating in a vehicle control system.
A further object of the invention is to provide a shunt that can be left coupled in parallel with the circuit it is to replace without interfering with the operation of that circuit.